1. Glenn Research Center at Lewis Field 1 NEONet 2006 Investigating 802.16 for Aeronautical Use Steven Bretmersky Cleveland State University March 1, 2006

2. Glenn Research Center at Lewis Field 2 Background The airport surface is a highly dynamic environment that encompasses many diverse users with different needs. Future operations will make more use of data communications and will require a wireless link. In the technology pre-screening phase of the Future Communication Study (a joint Eurocontrol / FAA study) 802.16 was identified as one possible enabling technology for the airport surface for ATC. This technology could benefit other surface users as well. This work investigates the possible uses of 802.16 for the airport surface.

3. Glenn Research Center at Lewis Field 3 Uses of a surface wireless network As a data link to aircraft for Air Traffic Control (ATC) and Aeronautical Operational Communications (AOC) messages As a data link for surface vehicles (fuel trucks, baggage carts, maintenance vehicles) As a backup link for existing ATC fixed surface systems (radar sites, voice radio sites, navaid sites) As a primary link for new surface systems located in remote or hard-to-reach areas (ASDE-X multilateration sensors, wake vortex sensors) As a network connection for airport staff (technicians in the field)

4. Glenn Research Center at Lewis Field 4 Wireless Surface Scenario Weather Radar ILS Aircraft Emergency Vehicles FAA Airlines Port Authority Technicians Fuel Truck Baggage Handlers RTR Radar Snow Removal Equipment ALS Wake Vortex Sensor RWSL ASDE-X Sensor

5. Glenn Research Center at Lewis Field 5 Current Communications Systems To Aircraft – VHF voice and character-based messaging system (ACARS) To surface vehicles – VHF voice to ATC, mobile radios To existing surface systems – copper, leased telco lines, microwave wireless links, and/or fiber. All existing surface systems use point-to-point analog interfaces (modems)

6. Glenn Research Center at Lewis Field 6 Future System Requirements High reliability Pre-emption / prioritization (QoS) Privacy / Security –Encryption –Authentication Mobility Operate in a protected band (safety of flight) –C-band identified as good candidate –MLS extension band (5.091 – 5.150 GHz) is unutilized and currently protected as aeronautical radionavigation

7. Glenn Research Center at Lewis Field 7 802.16 Flavors ✔✔ Mesh ✔✔✔ Mobility ✔✔✔✔ Spaced Time Coding (STC) ✔✔✔✔ Adaptive Antenna System (AAS) ✔✔✔✔ Automatic Repeat Request (ARQ) 10 – 66 GHz 2 - 11 GHz 2 - 11 GHz 2 - 11 GHz 2 - 11 GHz Frequency TDD FDD TDD FDD TDD FDD TDD FDD TDD Duplexing WirelessMAN-SC WirelessMAN-SCa WirelessMAN-OFDM WirelessMAN-OFDMA WirelessHUMAN

8. Glenn Research Center at Lewis Field 8 802.16 OFDM Waveform 8 Pilot Subcarriers –Used as reference for phase and amplitude 192 Data Subcarriers Combination of all subcarriers creates an OFDM symbol Pilot Subcarriers Data Subcarriers Guard Band

9. Glenn Research Center at Lewis Field 9 TDD Frame Structure Downlink Subframe UL BurstDL Burst iDL Burst 1UL Burst DL PHY PDUUL PHY PDU Uplink Subframe Frame Preamble Frame Control Header DL-MAP, UL-MAP, DCD, UCD Burst 1 MAC PDU 1 Burst 1 MAC PDU k Burst i MAC PDU 1 Burst i MAC PDU l Transmit/Receive Turnaround Gap Initial Ranging Contention Slot BW Request Contention Slot SS 1 PHY PDU Preamble SS 1 MAC PDU 1 SS 1 MAC PDU m SS x PHY PDU Preamble SS x MAC PDU 1 SS x MAC PDU n Receive/Transmit Turnaround Gap

10. Glenn Research Center at Lewis Field 10 802.16 on High Reliability 802.16 uses multiple modulations and FEC rates to offer best performance for link conditions. –Modulation / FEC selection is a tradeoff between robustness and data rate. –WirelessMAN-OFDM modulations: BPSK QPSK 16-QAM 64-QAM –WirelessMAN-OFDM FEC algorithms Reed-Solomon-Convolutional Code (RS-CC) at rates of 1/2, 2/3, and 3/4 Block Turbo Coding (BTC) at rates of 1/2, 3/5, 2/3, 3/4, 4/5, and 5/6 (optional) Convolutional Turbo Codes (CTC) at rates of 1/2, 2/3, and 3/4 (optional) 802.16 offers ARQ that can be enabled on a per- service-flow basis

11. Glenn Research Center at Lewis Field 11 802.16 on QoS 802.16 offers four types of services –Unsolicited Grant Service Real-time fixed-rate flows –Real Time Polled Service Real-time variable rate flows –Non-Real Time Polled Service –Best Effort Service QoS for real-time services –Priority (8 levels) –Tolerated jitter –Maximum tolerated latency –Minimum tolerated traffic rate 802.16 scheduler is not standardized

12. Glenn Research Center at Lewis Field 12 802.16 on Privacy / Security Key management –X.509 digital certificates –RSA public key encryption/authentication –Optional EAP authentication in 802.16e –HMAC with SHA-1 authentication Data encryption –DES with 56-bit keys –AES with 64 and 128 bit keys Data authentication –AES with 128-bit keys in 802.16e

13. Glenn Research Center at Lewis Field 13 802.16 on Mobility 802.16e adds the mobility component to the base standard –Designed to accommodate vehicular speeds (< 120 km/h) –Cannot support takeoff/landing speeds (~250 km/h), although this is not a big issue since the aircraft will likely be using the terminal area data link during these periods

14. Glenn Research Center at Lewis Field 14 Study Approach Identify surface applications and scenarios Create 802.16 OFDM model to use in OPNET simulations Identify and implement appropriate scheduling algorithm Evaluate scenario options and verify with simulations –Single vs. multiple systems –Channel size

15. Glenn Research Center at Lewis Field 15 802.16 Model Implementation of 802.16 P2MP protocols in progress –MAC Common Part Sublayer –Convergence Sublayer –Overhead from Privacy Sublayer –Overhead from OFDM PHY 802.16e extensions to be added in the future Creation of physical layer model to begin soon –Waiting for inputs from Ohio University Sounding Study Scope of Standard Service-Specific Convergence Sublayer (CS) MAC Common Part Sublayer (MAC CPS) Privacy Sublayer Physical Layer (PHY) Transmission Convergence (TC) CS SAP MAC SAP PHY SAP PHY MAC Scope of Model

16. Glenn Research Center at Lewis Field 16 Scheduling Algorithm Must determine when to grant bandwidth to services to meet QoS requirements –minimum rate –maximum latency –maximum jitter –priority Must poll subscribers at appropriate time Must take into account the current modulation and FEC rate being used by the subscriber

17. Glenn Research Center at Lewis Field 17 Bandwidth Options Channel bandwidth is configurable (between 1.25 and 25 MHz, 802.16e up to 5 MHz) Example (OFDM, G = 1/32) –1.25 MHz channel (minimum) BPSK with RS-CC ½ (most robust) –524 kbps raw data rate 64-QAM with RX-CC ¾ (least robust) –4.7 Mbps raw data rate –25 MHz channel BPSK with RS-CC ½ (most robust) –10.5 Mbps raw data rate 64-QAM with RX-CC ¾ (least robust) –94.2 Mbps raw data rate

18. Glenn Research Center at Lewis Field 18 Scenario Options Single system scenario –All nodes use same wireless channel(s) Multiple system scenarios –Separate wireless channels for fixed nodes and for mobiles –Separate point-to-multipoint and mesh channels

19. Glenn Research Center at Lewis Field 19 Comments?